example01:
    Do a real frequency calculation for Silicon. Generates 
    the real and imaginary parts of the selfenergy, and 
    the full spectral function using an analytic continuation for W(iw).
    
example02:
    Do an imaginary frequency calculation for Silicon. Calculates
    and the selfenergy as a function of imaginary frequency, and
    then analytically continues the selfenergy.
  
example03:
    Do an imaginary frequency calculation for MoS2, using godby-needs approximation.

example04:
    Do an imaginary frequency calculation for MoS2, using analytic continuation.

example05:
    Do a calculation of W (screened Coulomb interaction) and \mu, \mu*
    for MgB2 (This example is underconverged with respect to kpoints and 
    planewaves wavevectors).